A liquid jetting head uses a driving element such as a piezoelectric element to discharge ink or another liquid from a pressure chamber. The piezoelectric element comprises a piezoelectric film interposed between top and bottom electrodes. By applying a driving voltage to the electrodes, warping is produced such that the volume of the pressure chamber alters, and thus the liquid inside the cavity can be discharged. As liquid jetting heads become smaller, demands are being made for reductions in the film thickness of the piezoelectric film and the size of other parts.
In a liquid jetting head having a piezoelectric film that has been reduced in thickness, however, the diaphragm and piezoelectric film sometimes remain bent even when the voltage applied to the piezoelectric film is reduced to zero. It has been conjectured that one of the causes of this bending is that the effect of internal stress occurring in the diaphragm and piezoelectric film increases relative to reductions in the film thickness. When the diaphragm and piezoelectric film are bent in this manner, sufficient displacement cannot be obtained when a driving voltage is applied. It is possible that this problem will grow as the film thickness and size of liquid jetting heads continue to be reduced, and hence a solution is desirable in order to develop future liquid jetting heads.
An object of the present invention is to solve the problem described above by providing a liquid jetting head using a piezoelectric element that is capable of obtaining sufficient displacement through the application of a driving voltage.